The present invention relates to a telescopic member for mainly adjusting the height of legs of a desk, a chair, a table, a bed, etc., and also relates a cylindrical body for applying a frictional force to the telescopic operation of the telescopic member and a molded body that is installed in the cylindrical body.
FIG. 1 is a partial longitudinal cross-sectional view that shows the configuration of a conventional telescopic member. This telescopic member 100 has a step-wise height adjusting mechanism that has been disclosed in Japanese Patent Application Laid-Open No. 62-38967 (1987), and is attached to the lower end of each leg of, for example, a table T. In FIG. 1, for convenience of explanation, a screw portion S used for securing the leg, which is mounted at each corner of the bottom surface of the table T so as to stick out downward, is threadedly engaged directly with a screw hole 21a to be secured thereto. Here, the screw hole 21a is formed in the center portion of an end cap 21 welded to the upper end of its inner cylinder 2.
This telescopic member 100 is provided with an outer cylinder 3 that is externally fitted onto the inner cylinder 2 so as to allow it to slide freely inside thereof. A bottom cap 31 made of synthetic resin is attached to the lower end of the outer cylinder 3 with its one portion fitted therein. A screw 32 is inserted through the bottom cap 31 in the center thereof from the bottom side, (and threadedly engaged with a screw hole 34a formed in the base portion 34 of a pillar-shaped body 33 that is inserted into the inner cylinder 2 so that the base portion 34 is secured on the upper surface of the bottom cap 31.
The pillar-shaped body 33 is provided with an upright portion 35 formed on the upper side of the base portion 34 so as to stick out therefrom, and a plurality of engaging portions 36 provided as holes are formed in the upright portion 35 in its longitudinal direction (in the up-and-down direction in the FIG. 1) with appropriate intervals. A lock lever motion mechanism 22 is mounted with screws 23 to the inner circumferential surface of the inner cylinder 2 so as to oppose these engaging portions 36.
The lock lever motion mechanism 22 is provided with a frame body 24 that has a securing surface to the inner cylinder 2 in the vicinity of the center thereof and that has a channel shape in its cross-section when viewed from above or below, and the frame body 24 is arranged with its opening side of the channel shape facing the upright portion 35. Inside the frame body 24, a lock lever 25, which engages with the engaging portions 36, is swingably supported by a horizontal shaft 26 in the front to rear direction in its center portion shown in FIG. 1. FIG. 1 shows a state in which a pawl portion 25a, which is a lower end of the swing lever 25, is engaged with one of the engaging portions 36. The rotation of the lock lever 25 in the clockwise direction from the engaged state as shown in FIG. 1 is regulated by a contact of a holding portion 25b that is the other end of the lock lever 25 with the inner wall surface of the inner cylinder 2 of the frame body 24 on the securing side, and also regulated by a contact of its upper side moving end with one portion of a slider 27, as illustrated in FIG. 1; thus, its engaged state is maintained. Moreover, the rotation of the lock lever 25 in the counterclockwise direction is allowed although it goes against a spring 28 that applies a pressing force to the lock lever 25 in the opposite direction.
Therefore, as the inner cylinder 2 is slidden inside the outer cylinder 3 in the pull-out direction, that is, as the telescopic member 100 is extended, the lock lever motion mechanism 22 is raised relative to the outer cylinder 3 together with the inner cylinder 2 so that the pawl portion 25a of the lock lever 25 is allowed to contact the upper end of the engaging portion 36 with which it is currently engaged. As the inner cylinder 2 is further raised, the lock lever 25 is rotated counterclockwise in FIG. 1 against the pressing force of the spring 28, with the result that the engagement with the corresponding engaging portion 36 is released. Then, when the pawl portion 25a has reached the position of another engaging portion 36 right above of the above-mentioned engaging portion 36, the pressing force of the spring 28 allows the lock lever 25 to rotate clockwise, thereby again bringing the lock lever 25 into an engaged state with the new engaging portion 36.
As described above, the engagement between the lock lever 25 and the engaging portions 36 makes it possible to adjust the length of the telescopic member 100 with intervals in which the engaging portions 36 are provided. Moreover, as the lock lever motion mechanism 22 is raised with the inner cylinder 2 beyond the engaging portion 36 at the uppermost stage, the upper end of the slider 27 is allowed to contact a control piece 37a that is formed on an appropriate position above this engaging portion 36 so as to stick out toward the lock lever motion mechanism 22. The slider 27, which has its protruding portion 27a fitted to a longitudinally elongated hole 24a that is formed in the end walls of the channel shape of the frame body 24 in the thickness direction (in the front to rear direction in FIG. 1), is pressed downward by the control piece 37a along this elongated hole 24a. The slider 27, which has been pressed downward to the lower end position of the elongated hole 24a, forces the lock lever 25 to rotate counterclockwise against the pressing force of the spring 28, and also intervenes with the pawl portion 25a and the engaging portion 36 so as to prevent the engagement between them.
This arrangement allows the inner cylinder 2 to descend together with the lock lever motion mechanism 22, that is, to slide in the push-in direction. The lock lever motion mechanism 22, which descends together with the inner cylinder 2, has its slider 27 pushed up by a control piece 37b that is the same as the control piece 37a and that is formed in an appropriate position below the engaging portion 36 at the lowermost stage so as to stick out therefrom, through the motion opposite to that as described above; thus, the lock lever 25 is released from its engagement prevented state by the slider 27. Then, the lock lever motion mechanism 22 is again raised together with the inner cylinder 2 so that the lock lever 25 is engaged with the engaging portion 36 at the lowermost stage, and returned to the original state as shown in FIG. 1.
FIGS. 2A, 2B, and 2C are explanatory drawings that show the movements of a friction body in the conventional telescopic member. A cylindrical holder 4 is attached to the upper end of the outer cylinder 3 with its inner circumferential surface contacting the outer circumferential surface of the inner cylinder 2. This holder 4 maintains the inner cylinder 2 along its inner circumferential surface in a concentric manner with respect to the outer cylinder 3, and also applies frictional resistance to the movement of the inner cylinder 2 to a certain extent. Moreover, a braking chamber 42, which has a taper surface 41 opposing the outer circumferential surface of the inner cylinder 2, is placed along the inner circumferential surface of the holder 4, and a friction body 43 made of an O-ring is embedded in the braking chamber 42.
As illustrated in FIG. 2A, when the inner cylinder 2 is moved in the pull-out direction from the outer cylinder 3, the friction body 43 is moved upward until it contacts an upper-end moving end surface 44 (see FIGS. 2B and 2C) that is an upper end position of the braking chamber 42, following the movement of the inner cylinder 2. When the inner cylinder 2 is slidden in the push-in direction into the outer cylinder 3, as shown in FIG. 2B, the friction body 43 is moved to a lower position of the braking chamber 42 following the movement of the inner cylinder 2, and soon allowed to contact the taper surface 41. This contact allows the friction body 43 to roll while being sandwiched and deformed appropriately between the outer circumferential surface of the inner cylinder 2 and the taper surface 41, and this rolling movement provides an appropriate frictional force (braking force) when the inner cylinder 2 is moved in the push-in direction; thus, upon shortening the length of the telescopic member 100, it is possible to prevent the inner cylinder 2 from being abruptly moved in the push-in direction. Such a braking mechanism using the braking chamber 42 having the taper surface 41, and the frictional body 43 is disclosed in Japanese Utility Model Examined Patent Publication No. 25003 (1992) by the inventors of the present application.
FIG. 3A is a partial longitudinal cross-sectional view when seen from the right side that shows a holding portion for holding the pillar-shaped body, and FIG. 3B is a partial cross-sectional view taken along line D--D of FIG. 3A. At positions properly spaced in the longitudinal direction of the inner cylinder 2, holding portions 29, which are formed by means of pressing so as to protrude inside of the inner cylinder 2, are aligned so as to face each other at the respective positions in the longitudinal direction, and the total number of four of them are placed. These holding portions 29 press the upright portion 35 of the pillar-shaped body 33 to the inner circumferential surface of a semi-circular portion so as to secure it, the semi-circular portion being located in the inner cylinder 2 on the side opposite to the side on which the lock lever motion mechanism 22; thus, the pillar-shaped body 33, secured by a screw 32 (see FIG. 1), is prevented from rotating on the longitudinal axis so that the pawl portion 25a and the engaging hole 36 are held in such a position as to provide easy engagement of them.
However, in the above-mentioned conventional telescopic member 100, the braking chamber 42, placed along the holder 4, is formed into a reversed right triangle shape by a taper surface 41 in a cross-sectional view seen at one side; therefore, as the inner cylinder 2 is moved further in the push-in direction from the state shown in FIG. 2B, the friction body 43 is moved to a further lower position of the taper surface 41, that is, to a space in which the size of the braking chamber 42 becomes extremely smaller than the diameter of the friction body 43, as illustrated in FIG. 2C so that the deformation becomes too great to make a rolling movement, with the result that the frictional force to be applied to the inner cylinder 2 moving in the push-in direction tends to become unstable.
Moreover, since the holding portions 29 are formed in the inner cylinder 2 by means of pressing, the semicircular space between the paired holding portions 29 and the inner circumferential surface of the inner cylinder 2 tends to be comparatively poor in dimensional precision, and since this results in a greater range inside this space in which the upright portion 35 is allowed to freely move, it is not possible to prevent the rotation of the upright portion 35, thereby causing noise due to a contact between the inner circumferential surface of the inner cylinder 2 and the upright portion 35.
Moreover, in the attached state of the telescopic member 100 to the table T as illustrated in FIG. 1, for example, in the case when a rotational moment is applied to the table T so as to twist along in its plane direction, the inner cylinder 2 is rotated together with the table T, with the result that the holding portions 29 installed in the inner cylinder 2 twist the pillar-shaped body 33; this tends to cause a problem in which the table T becomes very unstable. This problem is particularly aggravated when this telescopic member 100 is applied to a so-called one-leg table T. For example, in most cases, since the base portion 34 of the pillar-shaped body 33 is secured on the floor through the bottom cap 31, etc., the rotational moment applied to the pillar-shaped body 33 is directly exerted on the base portion 34 causing its plastic deformation.